This invention deals with the separation of solid materials from a stream of fluid; more particularly, the straining of leaves, branches and other debris from river water before its use for cooling purposes in power generating plants, factories and the like.
Nearly all power generating plants require large quantities of water for condenser cooling purposes. As a result, many plants, especially those powered by fossil fuels, are located near rivers in order to take advantage of the plentiful supply of water. Before river water can be used to cool power generating equipment, however, the leaves, branches and other debris present in it must be removed. There are several currently employed methods of achieving this result. Each suffers from disadvantages over which the present invention offers substantial improvement. In typical existing systems used to strain debris from river water, the water flows through an intake tunnel and first passes through a set of bars which trap tree branches and other large debris. These bars are cleaned by lifting rakes whereupon the branches, etc., are hauled away for disposal. The water next passes through a moving conveyor-like screen which traps leaves and other small debris. To prevent clogging, the traveling screen continuously transports the trapped material from the river water flow past a jet of backwash water that dislodges the material from the screen into a trough.
The backwash water and debris from these systems may be returned to the river; however, where the return of the debris to the river is not desired, as in response to governmental regulations prohibiting such disposal, the debris must be separated from the backwash by another straining system so that it may be hauled away for further land disposal.
One system for separating debris from the backwash water utilizes a moving endless fine screen that traps the debris and carries it past a wire cleaning brush that dislodges the debris so that it will fall into a container or receptacle. To prevent freezing of the water and debris during cold weather operation, a canopy and heater are required. These systems, although reasonably effective, are complicated in construction and require continuous power to operate the screen and to heat the unit during freezing weather.
Other systems use basket-type strainers adapted to trap the debris in a fluid flow, allowing the clean water to drain and return to the river. The basket-type strainer must be periodically removed from the intake flow and emptied of debris. To facilitate emptying, the baskets are adapted to release their contents from the underside, through a hinged bottom panel. One of the disadvantages of these systems is that they require latches to secure the doors in the closed position while the basket is in use. The latching systems are easily clogged by debris, freeze during cold weather, and are damaged by workmen attempting to operate them. especially while clogged or frozen. Apart from maintenance difficulties, the latches add cost and complexity to the construction and necessitate additional steps in emptying the baskets.
Accordingly, it is an object of this invention to provide a bottom-emptying straining device which does not require latches or other mechanical fasteners to secure it in the closed position during straining.
Another object of this invention is to provide a straining device of the type described which will operate during freezing weather without the need for artifical heating.
Another object of this invention is to provide a straining device of the type described which is inexpensive, simple in construction and operation, and maintenance-free.
Further objects and advantages will become apparent from the following description and accompanying drawings.